back to 1st−4th century CE in oculists' stamps that were found mostly in Celtic areas, such as Gaul, Germany and Britain, which had an engraving of the name of the physician, the name of the special medicine or medical formula and the disease for which the medicine was to be used. Medieval alchemy used the Caduceus to represent preparations containing quicksilver, later known as mercury. Quicksilver (named ) was believed to be the basis of all substances and this element has been represented by the caduceus for many centuries. Medieval alchemists found parallels in the course of the soul through the unknown on its way to enlightenment, and the path from (unknown) illnesses back to health and life. Based on the medieval European use of the caduceus to signify pharmacy, Bavarian printer Erhard Ratdolt used the caduceus in his medical manuscripts from 1486 CE. Others followed (not uncontroversially, see section Modern times below). Sir William Butts, physician to Henry VIII, was the first physician to adopt it as his emblem. The rod of Asclepius, since the 5th century CE, resurfaced in 1544 CE. A publication of the medical writings of Avicenna, a Persian physician, had it at the frontispiece. Modern times Beginning with the 16th century there is limited evidence of the use of the caduceus in what is arguably a medical context. However, this evidence is also ambiguous. In some cases it is clear that the caduceus symbolized wisdom, without any specific medical connotations. The caduceus appears in a general medical context in the printer's device used by the Swiss medical printer Johann Frobenius (1460–1527), who depicted the staff entwined with serpents and surmounted by a dove, with a biblical epigraph in Greek, "Be ye therefore wise as serpents and harmless as doves" (Matthew 10:16, here in the KJV translation), in keeping with the connotations of the caduceus as a symbol of messengers and publishers based on the association of Hermes or Mercury with eloquence and negotiation. Friedlander observed that Frobenius could hardly be considered a medical printer, as had previously been asserted, noting that in a review of 257 of the works bearing this printer's device only one was related to medicine. Similar use of the caduceus in printers' marks continues to the present day, with companies including F. A. Davis Company still using the symbol as an element of their insignia. There are a few other examples